5 files changed, 190 insertions, 2 deletions

diff --git a/arch/Kconfig b/arch/Kconfig
index 68d827b7ae82..2a83a3f6a615 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -228,6 +228,13 @@ config HAVE_PERF_REGS
           Support selective register dumps for perf events. This includes
           bit-mapping of each registers and a unique architecture id.
 
+config HAVE_PERF_USER_STACK_DUMP
+        bool
+        help
+          Support user stack dumps for perf event samples. This needs
+          access to the user stack pointer which is not unified across
+          architectures.
+
 config HAVE_ARCH_JUMP_LABEL
         bool
 
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 3fab6ec9edc4..a2d19ee750ca 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -61,6 +61,7 @@ config X86
         select PERF_EVENTS
         select HAVE_PERF_EVENTS_NMI
         select HAVE_PERF_REGS
+        select HAVE_PERF_USER_STACK_DUMP
         select ANON_INODES
         select HAVE_ALIGNED_STRUCT_PAGE if SLUB && !M386
         select HAVE_CMPXCHG_LOCAL if !M386
diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index 8a73f75beb16..d1d25f6a5e24 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -131,8 +131,9 @@ enum perf_event_sample_format {
         PERF_SAMPLE_RAW                         = 1U << 10,
         PERF_SAMPLE_BRANCH_STACK                = 1U << 11,
         PERF_SAMPLE_REGS_USER                   = 1U << 12,
+        PERF_SAMPLE_STACK_USER                  = 1U << 13,
 
-        PERF_SAMPLE_MAX = 1U << 13,             /* non-ABI */
+        PERF_SAMPLE_MAX = 1U << 14,             /* non-ABI */
 };
 
 /*
@@ -205,6 +206,7 @@ enum perf_event_read_format {
 #define PERF_ATTR_SIZE_VER1     72      /* add: config2 */
 #define PERF_ATTR_SIZE_VER2     80      /* add: branch_sample_type */
 #define PERF_ATTR_SIZE_VER3     88      /* add: sample_regs_user */
+#define PERF_ATTR_SIZE_VER4     96      /* add: sample_stack_user */
 
 /*
  * Hardware event_id to monitor via a performance monitoring event:
@@ -289,6 +291,14 @@ struct perf_event_attr {
          * See asm/perf_regs.h for details.
          */
         __u64   sample_regs_user;
+
+        /*
+         * Defines size of the user stack to dump on samples.
+         */
+        __u32   sample_stack_user;
+
+        /* Align to u64. */
+        __u32   __reserved_2;
 };
 
 /*
@@ -568,6 +578,10 @@ enum perf_event_type {
          *
          *      { u64                   abi; # enum perf_sample_regs_abi
          *        u64                   regs[weight(mask)]; } && PERF_SAMPLE_REGS_USER
+         *
+         *      { u64                   size;
+         *        char                  data[size];
+         *        u64                   dyn_size; } && PERF_SAMPLE_STACK_USER
          * };
          */
         PERF_RECORD_SAMPLE                      = 9,
@@ -1160,6 +1174,7 @@ struct perf_sample_data {
         struct perf_raw_record          *raw;
         struct perf_branch_stack        *br_stack;
         struct perf_regs_user           regs_user;
+        u64                             stack_user_size;
 };
 
 static inline void perf_sample_data_init(struct perf_sample_data *data,
@@ -1172,6 +1187,7 @@ static inline void perf_sample_data_init(struct perf_sample_data *data,
         data->period = period;
         data->regs_user.abi = PERF_SAMPLE_REGS_ABI_NONE;
         data->regs_user.regs = NULL;
+        data->stack_user_size = 0;
 }
 
 extern void perf_output_sample(struct perf_output_handle *handle,
diff --git a/kernel/events/core.c b/kernel/events/core.c
index d3ce97525b9f..2ba890450d15 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -36,6 +36,7 @@
 #include <linux/perf_event.h>
 #include <linux/ftrace_event.h>
 #include <linux/hw_breakpoint.h>
+#include <linux/mm_types.h>
 
 #include "internal.h"
 
@@ -3787,6 +3788,101 @@ static void perf_sample_regs_user(struct perf_regs_user *regs_user,
         }
 }
 
+/*
+ * Get remaining task size from user stack pointer.
+ *
+ * It'd be better to take stack vma map and limit this more
+ * precisly, but there's no way to get it safely under interrupt,
+ * so using TASK_SIZE as limit.
+ */
+static u64 perf_ustack_task_size(struct pt_regs *regs)
+{
+        unsigned long addr = perf_user_stack_pointer(regs);
+
+        if (!addr || addr >= TASK_SIZE)
+                return 0;
+
+        return TASK_SIZE - addr;
+}
+
+static u16
+perf_sample_ustack_size(u16 stack_size, u16 header_size,
+                        struct pt_regs *regs)
+{
+        u64 task_size;
+
+        /* No regs, no stack pointer, no dump. */
+        if (!regs)
+                return 0;
+
+        /*
+         * Check if we fit in with the requested stack size into the:
+         * - TASK_SIZE
+         *   If we don't, we limit the size to the TASK_SIZE.
+         *
+         * - remaining sample size
+         *   If we don't, we customize the stack size to
+         *   fit in to the remaining sample size.
+         */
+
+        task_size  = min((u64) USHRT_MAX, perf_ustack_task_size(regs));
+        stack_size = min(stack_size, (u16) task_size);
+
+        /* Current header size plus static size and dynamic size. */
+        header_size += 2 * sizeof(u64);
+
+        /* Do we fit in with the current stack dump size? */
+        if ((u16) (header_size + stack_size) < header_size) {
+                /*
+                 * If we overflow the maximum size for the sample,
+                 * we customize the stack dump size to fit in.
+                 */
+                stack_size = USHRT_MAX - header_size - sizeof(u64);
+                stack_size = round_up(stack_size, sizeof(u64));
+        }
+
+        return stack_size;
+}
+
+static void
+perf_output_sample_ustack(struct perf_output_handle *handle, u64 dump_size,
+                          struct pt_regs *regs)
+{
+        /* Case of a kernel thread, nothing to dump */
+        if (!regs) {
+                u64 size = 0;
+                perf_output_put(handle, size);
+        } else {
+                unsigned long sp;
+                unsigned int rem;
+                u64 dyn_size;
+
+                /*
+                 * We dump:
+                 * static size
+                 *   - the size requested by user or the best one we can fit
+                 *     in to the sample max size
+                 * data
+                 *   - user stack dump data
+                 * dynamic size
+                 *   - the actual dumped size
+                 */
+
+                /* Static size. */
+                perf_output_put(handle, dump_size);
+
+                /* Data. */
+                sp = perf_user_stack_pointer(regs);
+                rem = __output_copy_user(handle, (void *) sp, dump_size);
+                dyn_size = dump_size - rem;
+
+                perf_output_skip(handle, rem);
+
+                /* Dynamic size. */
+                perf_output_put(handle, dyn_size);
+        }
+}
+
 static void __perf_event_header__init_id(struct perf_event_header *header,
                                          struct perf_sample_data *data,
                                          struct perf_event *event)
@@ -4064,6 +4160,11 @@ void perf_output_sample(struct perf_output_handle *handle,
                                                 mask);
                 }
         }
+
+        if (sample_type & PERF_SAMPLE_STACK_USER)
+                perf_output_sample_ustack(handle,
+                                          data->stack_user_size,
+                                          data->regs_user.regs);
 }
 
 void perf_prepare_sample(struct perf_event_header *header,
@@ -4129,6 +4230,35 @@ void perf_prepare_sample(struct perf_event_header *header,
 
                 header->size += size;
         }
+
+        if (sample_type & PERF_SAMPLE_STACK_USER) {
+                /*
+                 * Either we need PERF_SAMPLE_STACK_USER bit to be allways
+                 * processed as the last one or have additional check added
+                 * in case new sample type is added, because we could eat
+                 * up the rest of the sample size.
+                 */
+                struct perf_regs_user *uregs = &data->regs_user;
+                u16 stack_size = event->attr.sample_stack_user;
+                u16 size = sizeof(u64);
+
+                if (!uregs->abi)
+                        perf_sample_regs_user(uregs, regs);
+
+                stack_size = perf_sample_ustack_size(stack_size, header->size,
+                                                     uregs->regs);
+
+                /*
+                 * If there is something to dump, add space for the dump
+                 * itself and for the field that tells the dynamic size,
+                 * which is how many have been actually dumped.
+                 */
+                if (stack_size)
+                        size += sizeof(u64) + stack_size;
+
+                data->stack_user_size = stack_size;
+                header->size += size;
+        }
 }
 
 static void perf_event_output(struct perf_event *event,
@@ -6205,8 +6335,26 @@ static int perf_copy_attr(struct perf_event_attr __user *uattr,
                 }
         }
 
-        if (attr->sample_type & PERF_SAMPLE_REGS_USER)
+        if (attr->sample_type & PERF_SAMPLE_REGS_USER) {
                 ret = perf_reg_validate(attr->sample_regs_user);
+                if (ret)
+                        return ret;
+        }
+
+        if (attr->sample_type & PERF_SAMPLE_STACK_USER) {
+                if (!arch_perf_have_user_stack_dump())
+                        return -ENOSYS;
+
+                /*
+                 * We have __u32 type for the size, but so far
+                 * we can only use __u16 as maximum due to the
+                 * __u16 sample size limit.
+                 */
+                if (attr->sample_stack_user >= USHRT_MAX)
+                        ret = -EINVAL;
+                else if (!IS_ALIGNED(attr->sample_stack_user, sizeof(u64)))
+                        ret = -EINVAL;
+        }
 
 out:
         return ret;
diff --git a/kernel/events/internal.h b/kernel/events/internal.h
index ce7bdfc1d045..d56a64c99a8b 100644
--- a/kernel/events/internal.h
+++ b/kernel/events/internal.h
@@ -158,4 +158,20 @@ static inline void put_recursion_context(int *recursion, int rctx)
         recursion[rctx]--;
 }
 
+#ifdef CONFIG_HAVE_PERF_USER_STACK_DUMP
+static inline bool arch_perf_have_user_stack_dump(void)
+{
+        return true;
+}
+
+#define perf_user_stack_pointer(regs) user_stack_pointer(regs)
+#else
+static inline bool arch_perf_have_user_stack_dump(void)
+{
+        return false;
+}
+
+#define perf_user_stack_pointer(regs) 0
+#endif /* CONFIG_HAVE_PERF_USER_STACK_DUMP */
+
 #endif /* _KERNEL_EVENTS_INTERNAL_H */